Power tracker for multiple transmit signals sent simultaneously

ABSTRACT

Techniques for generating a power tracking supply voltage for a circuit (e.g., a power amplifier) are disclosed. The circuit may process multiple transmit signals being sent simultaneously on multiple carriers at different frequencies. In one exemplary design, an apparatus includes a power tracker and a power supply generator. The power tracker determines a power tracking signal based on inphase (I) and quadrature (Q) components of a plurality of transmit signals being sent simultaneously. The power supply generator generates a power supply voltage based on the power tracking signal. The apparatus may further include a power amplifier (PA) that amplifies a modulated radio frequency (RF) signal based on the power supply voltage and provides an output RF signal.

BACKGROUND

I. Field

The present disclosure relates generally to electronics, and morespecifically to techniques for generating a power supply voltage for acircuit such as an amplifier.

II. Background

A wireless device (e.g., a cellular phone or a smartphone) in a wirelesscommunication system may transmit and receive data for two-waycommunication. The wireless device may include a transmitter for datatransmission and a receiver for data reception. For data transmission,the transmitter may process (e.g., encode and modulate) data to generateoutput samples. The transmitter may further condition (e.g., convert toanalog, filter, amplify, and frequency upconvert) the output samples togenerate a modulated radio frequency (RF) signal, amplify the modulatedRF signal to obtain an output RF signal having the proper transmit powerlevel, and transmit the output RF signal via an antenna to a basestation. For data reception, the receiver may obtain a received RFsignal via the antenna and may amplify and process the received RFsignal to recover data sent by the base station.

The transmitter typically includes a power amplifier (PA) to providehigh transmit power for the output RF signal. The power amplifier shouldbe able to provide high transmit power and have high power-addedefficiency (PAE).

SUMMARY

Techniques for generating a power tracking supply voltage for a circuit(e.g., a power amplifier) that processes multiple transmit signals sentsimultaneously are disclosed herein. The multiple transmit signals maycomprise transmissions sent simultaneously on multiple carriers atdifferent frequencies.

In one exemplary design, an apparatus includes a power tracker and apower supply generator. The power tracker determines a power trackingsignal based on inphase (I) and quadrature (Q) components of a pluralityof transmit signals being sent simultaneously, as described below. Thepower supply generator generates a power supply voltage based on thepower tracking signal. The apparatus may further include a poweramplifier that amplifies a modulated RF signal based on the power supplyvoltage and provides an output RF signal.

Various aspects and features of the disclosure are described in furtherdetail below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a wireless device communicating with a wireless system.

FIGS. 2A to 2D show four examples of carrier aggregation.

FIG. 3 shows a block diagram of the wireless device in FIG. 1.

FIG. 4 shows a transmit module comprising a separate power amplifierwith separate power tracking for each transmit signal.

FIGS. 5 and 6 show two designs of a transmit module comprising a singlepower amplifier with power tracking for all transmit signals.

FIGS. 7A and 7B show power tracking for two and three transmit signals,respectively.

FIGS. 8 and 9 show a design of a power supply generator with powertracking.

FIG. 10 shows a process for generating a power supply voltage with powertracking.

DETAILED DESCRIPTION

The word “exemplary” is used herein to mean “serving as an example,instance, or illustration.” Any design described herein as “exemplary”is not necessarily to be construed as preferred or advantageous overother designs.

Techniques for generating a power tracking supply voltage for a circuit(e.g., a power amplifier) that processes multiple transmit signals sentsimultaneously are disclosed herein. The techniques may be used forvarious electronic devices such as wireless communication devices.

FIG. 1 shows a wireless device 110 communicating with a wirelesscommunication system 120. Wireless system 120 may be a Long TermEvolution (LTE) system, a Code Division Multiple Access (CDMA) system, aGlobal System for Mobile Communications (GSM) system, a wireless localarea network (WLAN) system, or some other wireless system. A CDMA systemmay implement Wideband CDMA (WCDMA), CDMA 1X, Time Division SynchronousCDMA (TD-SCDMA), or some other version of CDMA. For simplicity, FIG. 1shows wireless system 120 including two base stations 130 and 132 andone system controller 140. In general, a wireless system may include anynumber of base stations and any set of network entities.

Wireless device 110 may also be referred to as a user equipment (UE), amobile station, a terminal, an access terminal, a subscriber unit, astation, etc. Wireless device 110 may be a cellular phone, a smartphone,a tablet, a wireless modem, a personal digital assistant (PDA), ahandheld device, a laptop computer, a smartbook, a netbook, a cordlessphone, a wireless local loop (WLL) station, a Bluetooth device, etc.Wireless device 110 may be capable of communicating with wireless system120. Wireless device 110 may also be capable of receiving signals frombroadcast stations (e.g., a broadcast station 134), signals fromsatellites (e.g., a satellite 150) in one or more global navigationsatellite systems (GNSS), etc. Wireless device 110 may support one ormore radio technologies for wireless communication such as LTE, WCDMA,CDMA 1X, TD-SCDMA, GSM, 802.11, etc.

Wireless device 110 may be able to operate in low-band (LB) coveringfrequencies lower than 1000 megahertz (MHz), mid-band (MB) coveringfrequencies from 1000 MHz to 2300 MHz, and/or high-band (HB) coveringfrequencies higher than 2300 MHz. For example, low-band may cover 698 to960 MHz, mid-band may cover 1475 to 2170 MHz, and high-band may cover2300 to 2690 MHz and 3400 to 3800 MHz. Low-band, mid-band, and high-bandrefer to three groups of bands (or band groups), with each band groupincluding a number of frequency bands (or simply, “bands”). Each bandmay cover up to 200 MHz and may include one or more carriers. Eachcarrier may cover up to 20 MHz in LTE. LTE Release 11 supports 35 bands,which are referred to as LTE/UMTS bands and are listed in 3GPP TS36.101.

Wireless device 110 may support carrier aggregation, which is operationon multiple carriers. Carrier aggregation may also be referred to asmulti-carrier operation. Wireless device 110 may be configured with upto 5 carriers in one or two bands in LTE Release 11.

In general, carrier aggregation (CA) may be categorized into twotypes—intra-band CA and inter-band CA. Intra-band CA refers to operationon multiple carriers within the same band. Inter-band CA refers tooperation on multiple carriers in different bands.

FIG. 2A shows an example of contiguous intra-band CA. In the exampleshown in FIG. 2A, wireless device 110 is configured with threecontiguous carriers in one band in low-band. Wireless device 110 maysend and/or receive transmissions on the three contiguous carriers inthe same band.

FIG. 2B shows an example of non-contiguous intra-band CA. In the exampleshown in FIG. 2B, wireless device 110 is configured with threenon-contiguous carriers in one band in low-band. The carriers may beseparated by 5 MHz, 10 MHz, or some other amount. Wireless device 110may send and/or receive transmissions on the three non-contiguouscarriers in the same band.

FIG. 2C shows an example of inter-band CA in the same band group. In theexample shown in FIG. 2C, wireless device 110 is configured with threecarriers in two bands in low-band. Wireless device 110 may send and/orreceive transmissions on the three carriers in different bands in thesame band group.

FIG. 2D shows an example of inter-band CA in different band groups. Inthe example shown in FIG. 2D, wireless device 110 is configured withthree carriers in two bands in different band groups, which include twocarriers in one band in low-band and one carrier in another band inmid-band. Wireless device 110 may send and/or receive transmissions onthe three carriers in different bands in different band groups.

FIGS. 2A to 2D show four examples of carrier aggregation. Carrieraggregation may also be supported for other combinations of bands andband groups.

FIG. 3 shows a block diagram of an exemplary design of wireless device110 in FIG. 1. In this exemplary design, wireless device 110 includes adata processor/controller 310, a transceiver 320 coupled to a primaryantenna 390, and a transceiver 322 coupled to a secondary antenna 392.Transceiver 320 includes K transmitters 330 pa to 330 pk, L receivers380 pa to 380 pl, and an antenna interface circuit 370 to supportmultiple bands, carrier aggregation, multiple radio technologies, etc. Kand L may each be any integer value of one or greater. Transceiver 322includes M transmitters 330 sa to 330 sm, N receivers 380 sa to 380 sn,and an antenna interface circuit 372 to support multiple bands, carrieraggregation, multiple radio technologies, receive diversity,multiple-input multiple-output (MIMO) transmission, etc. M and N mayeach be any integer value of one or greater.

In the exemplary design shown in FIG. 3, each transmitter 330 includes atransmit circuit 340 and a power amplifier (PA) 360. For datatransmission, data processor 310 processes (e.g., encodes and symbolmaps) data to be transmitted to obtain modulation symbols. Dataprocessor 310 further processes the modulation symbols (e.g., for OFDM,SC-FDMA, CDMA, or some other modulation technique) and provides I and Qsamples for each transmit signal to be sent by wireless device 110. Atransmit signal is a signal comprising a transmission on one or morecarriers, a transmission on one or more frequency channels, etc. Dataprocessor 310 provides the I and Q samples for one or more transmitsignals to one or more selected transmitters. The description belowassumes that transmitter 330 pa is a transmitter selected to send onetransmit signal. Within transmitter 330 pa, transmit circuit 340 paconverts I and Q samples to I and Q analog output signals, respectively.Transmit circuit 340 pa further amplifies, filters, and upconverts the Iand Q analog output signals from baseband to RF and provides a modulatedRF signal. Transmit circuit 340 pa may include digital-to-analogconverters (DACs), amplifiers, filters, mixers, matching circuits, anoscillator, a local oscillator (LO) generator, a phase-locked loop(PLL), etc. A PA 360 pa receives and amplifies the modulated RF signaland provides an output RF signal having the proper transmit power level.The output RF signal is routed through antenna interface circuit 370 andtransmitted via antenna 390. Antenna interface circuit 370 may includeone or more filters, duplexers, diplexers, switches, matching circuits,directional couplers, etc. Each remaining transmitter 330 intransceivers 320 and 322 may operate in similar manner as transmitter330 pa.

In the exemplary design shown in FIG. 3, each receiver 380 includes alow noise amplifier (LNA) 382 and a receive circuit 384. For datareception, antenna 390 receives signals from base stations and/or othertransmitter stations and provides a received RF signal, which is routedthrough antenna interface circuit 370 and provided to a selectedreceiver. The description below assumes that receiver 380 pa is theselected receiver. Within receiver 380 pa, an LNA 382 pa amplifies thereceived RF signal and provides an amplified RF signal. A receivecircuit 384 pa downconverts the amplified RF signal from RF to baseband,amplifies and filters the downconverted signal, and provides an analoginput signal to data processor 310. Receive circuit 384 pa may includemixers, filters, amplifiers, matching circuits, an oscillator, an LOgenerator, a PLL, etc. Each remaining receiver 380 in transceivers 320and 322 may operate in similar manner as receiver 380 pa.

FIG. 3 shows an exemplary design of transmitters 330 and receivers 380.A transmitter and a receiver may also include other circuits not shownin FIG. 3, such as filters, matching circuits, etc. All or a portion oftransceivers 320 and 322 may be implemented on one or more analogintegrated circuits (ICs), RF ICs (RFICs), mixed-signal ICs, etc. Forexample, transmit circuits 340, LNAs 382, and receive circuits 384 maybe implemented on one module, which may be an RFIC, etc. Antennainterface circuits 370 and 372 and PAs 360 may be implemented on anothermodule, which may be a hybrid module, etc. The circuits in transceivers320 and 322 may also be implemented in other manners.

Data processor/controller 310 may perform various functions for wirelessdevice 110. For example, data processor 310 may perform processing fordata being transmitted via transmitters 330 and data being received viareceivers 380. Controller 310 may control the operation of transmitcircuits 340, PAs 360, LNAs 382, receive circuits 384, antenna interfacecircuits 370 and 372, or a combination thereof. A memory 312 may storeprogram codes and data for data processor/controller 310. Dataprocessor/controller 310 may be implemented on one or more applicationspecific integrated circuits (ASICs) and/or other ICs.

Wireless device 110 may send multiple transmit signals simultaneously.In one design, the multiple transmit signals may be for transmissions onmultiple contiguous or non-contiguous carriers with intra-band CA.,e.g., as shown in FIG. 2A or 2B. For example, each transmit signal maycomprise a transmission sent on one carrier. In another design, themultiple transmit signals may be for transmissions on multiple frequencychannels to the same wireless system. In yet another design, themultiple transmit signals may be for transmissions sent to differentwireless systems (e.g., LTE and WLAN). In any case, data to be sent ineach transmit signal may be processed (e.g., encoded, symbol mapped, andmodulated) separately to generate I and Q samples for that transmitsignal. Each transmit signal may be conditioned by a respective transmitcircuit 340 and amplified by a respective PA 360 to generate an outputRF signal for that transmit signal.

A PA may receive a modulated RF signal and a power supply voltage andmay generate an output RF signal. The output RF signal typically tracksthe modulated RF signal and has a time-varying envelope. The powersupply voltage should be higher than the amplitude of the output RFsignal at all times in order to avoid clipping the output RF signal,which would then cause intermodulation distortion (IMD) that may degradeperformance. The difference between the power supply voltage and theenvelope of the output RF signal represents wasted power that isdissipated by the PA instead of delivered to an output load.

It may be desirable to generate a power supply voltage for a PA suchthat good performance and good efficiency can be obtained. This may beachieved by generating the power supply voltage for the PA with powertracking so that the power supply voltage can track the envelope of anoutput RF signal from the PA.

FIG. 4 shows a design of a transmit module 400 supporting simultaneoustransmission of multiple (K) transmit signals with a separate PA andseparate power tracking for each transmit signal. Transmit module 400includes K transmitters 430 a to 430 k that can simultaneously process Ktransmit signals, with each transmitter 430 processing one transmitsignal. Each transmitter 430 includes a transmit circuit 440, a PA 460,and a power tracking supply generator 480.

Transmitter 430 a receives I₁ and Q₁ samples for a first transmit signaland generates a first output RF signal for the first transmit signal.The I₁ and Q₁ samples are provided to both transmit circuit 440 a andvoltage generator 480 a. Within transmit circuit 440 a, the I₁ and Q₁samples are converted to I and Q analog signals by DACs 442 a and 443 a,respectively. The I analog signal is filtered by a lowpass filter 444 a,amplified by an amplifier (Amp) 446 a, and upconverted from baseband toRF by a mixer 448 a. Similarly, the Q analog signal is filtered by alowpass filter 445 a, amplified by an amplifier 447 a, and upconvertedfrom baseband to RF by a mixer 449 a. Mixers 448 a and 449 a performupconversion for the first transmit signal based on I and Q LO signals(ILO₁ and QLO₁) at a center RF frequency of the first transmit signal. Asummer 450 a sums the I and Q upconverted signals from mixers 448 a and449 a to obtain a modulated RF signal, which is provided to PA 460 a.

Within voltage generator 480 a, a power tracker 482 a receives the I₁and Q₁ samples for the first transmit signal, computes the power of thefirst transmit signal based on the I₁ and Q₁ samples, and provides adigital power tracking signal to a DAC 484 a. DAC 484 a converts thedigital power tracking signal to analog and provides an analog powertracking signal. A power supply generator 486 a receives the analogpower tracking signal and generates a power supply voltage for PA 460 a.PA 460 a amplifies the modulated RF signal from transmit circuit 440 ausing the power supply voltage from supply generator 486 a and providesthe first output RF signal for the first transmit signal.

Each remaining transmitter 430 may similarly process I and Q samples fora respective transmit signal and may provide an output RF signal for thetransmit signal. Up to K PAs 460 a to 460 k may provide up to K outputRF signals at different RF frequencies for up to K transmit signalsbeing sent simultaneously. A summer 462 receives the output RF signalsbeing sent simultaneously, sums the output RF signals, and provides afinal output RF signal, which is routed through a duplexer 470 andtransmitted via an antenna 490.

As shown in FIG. 4, power tracking may be used to improve the efficiencyof PAs 460 a to 460 k. Each transmit signal may be processed by arespective transmitter 430 using a separate sets of mixers 448 and 449and PA 460. Multiple transmit signals may be sent on differentfrequencies (e.g., different carriers) and hence may have increasedenvelope bandwidth. The increased envelope bandwidth may be addressed byusing a separate transmitter 430 for each transmit signal. Eachtransmitter 430 may then handle the envelope bandwidth of one transmitsignal. However, operating multiple transmitters 430 concurrently formultiple transmit signals may result in more circuits, higher powerconsumption, and increased cost, all of which are undesirable.

In an aspect of the present disclosure, a single PA with power trackingmay be used to generate a single output RF signal for multiple transmitsignals being sent simultaneously. A single power supply voltage may begenerated for the PA to track the power of all transmit signals beingsent simultaneously. This may reduce the number of circuit components,reduce power consumption, and provide other advantages.

FIG. 5 shows a design of a transmit module 500 supporting simultaneoustransmission of multiple (K) transmit signals with a single PA and powertracking for all transmit signals. Transmit module 500 performsfrequency upconversion separately for each transmit signal in the analogdomain and sums the resultant upconverted RF signals for all transmitsignals. Transmit module 500 includes K transmit circuits 540 a to 540 kthat can simultaneously process K transmit signals, with each transmitcircuit 540 processing one transmit signal. Transmit module 500 furtherincludes a summer 552, a PA 560, a duplexer 570, and a power trackingsupply generator 580.

Transmit circuit 540 a receives I₁ and Q₁ samples for a first transmitsignal and generates a first upconverted RF signal for the firsttransmit signal. The I₁ and Q₁ samples are provided to both transmitcircuit 540 a and voltage generator 580. Within transmit circuit 540 a,the I₁ and Q₁ samples are converted to I and Q analog signals by DACs542 a and 543 a, respectively. The I and Q analog signals are filteredby lowpass filters 544 a and 545 a, amplified by amplifiers 546 a and547 a, upconverted from baseband to RF by mixers 548 a and 549 a, andsummed by a summer 550 a to generate the first upconverted RF signal.Mixers 548 a and 549 a perform upconversion for the first transmitsignal based on I and Q LO signals at a center RF frequency of the firsttransmit signal.

Each remaining transmit circuit 540 may similarly process I and Qsamples for a respective transmit signal and may provide an upconvertedRF signal for the transmit signal. Up to K transmit circuits 540 a to540 k may provide up to K upconverted RF signals at different RFfrequencies for up to K transmit signals being sent simultaneously. Asummer 552 receives the upconverted RF signals from transmit circuits540 a to 540 k, sums the upconverted RF signals, and provides amodulated RF signal to PA 560.

Within voltage generator 580, a power tracker 582 receives I₁ to I_(K)samples and Q₁ to Q_(K) samples for all transmit signals being sentsimultaneously. Power tracker 582 computes the overall power of alltransmit signals based on the I and Q samples for these transmit signalsand provides a digital power tracking signal to a DAC 584. DAC 584converts the digital power tracking signal to analog and provides ananalog power tracking signal for all transmit signals. Although notshown in FIG. 5, a lowpass filter may receive and filter an outputsignal from DAC 584 and provide the analog power tracking signal. Apower supply generator 586 receives the analog power tracking signal andgenerates a power supply voltage for PA 560.

PA 560 amplifies the modulated RF signal from summer 552 using the powersupply voltage from supply generator 586. PA 560 provides an output RFsignal for all transmit signals being sent simultaneously. The output RFsignal is routed through duplexer 570 and transmitted via antenna 590.

FIG. 6 shows a design of a transmit module 502 supporting simultaneoustransmission of multiple (K) transmit signals with a single PA and powertracking for all transmit signals. Transmit module 502 digitallyupconverts each transmit signal to an intermediate frequency (IF) in thedigital domain, sums the resultant upconverted IF signals for alltransmit signals, and performs frequency upconversion from IF to RF forall transmit signals together in the analog domain. Transmit module 502includes a digital modulator 520, a transmit circuit 540, PA 560,duplexer 570, and power tracking supply generator 580.

Digital modulator 520 receives I and Q samples for all transmit signalsand generates a modulated IF signal for all transmit signals. Withindigital modulator 520, the I₁ and Q₁ samples for the first transmitsignal are upconverted to a first IF frequency by multipliers 522 a and523 a, respectively, based on C_(I1) and C_(Q1)) digital LO signals. TheI and Q samples for each remaining transmit signal are upconverted to adifferent IF frequency by multipliers 522 and 523, respectively, forthat transmit signal. The IF frequencies of the K transmit signals maybe selected based on the final RF frequencies of the K transmit signals.A summer 524 sums the outputs of all K multipliers 522 a to 522 k andprovides an I modulated signal. Similarly, a summer 525 sums the outputsof all K multipliers 523 a to 523 k and provides a Q modulated signal.The I and Q modulated signals from summers 524 and 525 form themodulated IF signal for all transmit signals.

Transmit circuit 540 receives I and Q modulated signals from digitalmodulator 520 and generates a modulated RF signal for all transmitsignals. Within transmit circuit 540, the I and Q modulated signals areconverted to I and Q analog signals by DACs 542 and 543, respectively.The I and Q analog signals are filtered by lowpass filters 544 and 545,amplified by amplifiers 546 and 547, upconverted from IF to RF by mixers548 and 549, and summed by a summer 550 to generate the modulated RFsignal. Mixers 548 and 549 perform upconversion for the modulated IFsignal based on I and Q LO signals at a suitable frequency so that the Ktransmit signals are upconverted to their proper RF frequencies.

Power tracking voltage generator 580 receives the I₁ to I_(K) samplesand the Q₁ to Q_(K) samples for all transmit signals being sentsimultaneously. Voltage generator 580 generates a power supply voltagefor PA 560 based on the I and Q samples. PA 560 amplifies the modulatedRF signal from transmit circuit 540 using the power supply voltage fromsupply generator 580. PA 560 provides an output RF signal for alltransmit signals being sent simultaneously. The output RF signal isrouted through duplexer 570 and transmitted via antenna 590.

FIGS. 5 and 6 show two exemplary designs of a transmit module supportingsimultaneous transmission of multiple transmit signals with a single PAand power tracking for all transmit signals. Multiple transmit signalsmay also be sent with a single PA and power tracking in other manners.For example, polar modulation may be used instead of quadraturemodulation, which is shown in FIGS. 5 and 6.

Power tracker 582 may compute the digital power tracking signal based onthe I and Q samples for all transmit signals in various manners. In onedesign, the digital power tracking signal may be computed as follows:p(t)=√{square root over (K)}·√{square root over (I₁ ²(t)+Q ₁ ²(t)+ . . .+I _(K) ²(t)+Q _(K) ²(t))},   Eq (1)where I_(k)(t) and Q_(k)(t) denote the I and Q samples for the k-thtransmit signal in sample period t, for k=1, . . . , K, and

-   -   p(t) denotes the digital power tracking signal in sample period        t.

The quantity I_(k) ²(t)+Q_(k) ²(t) denotes the power of the k-thtransmit signal in sample period t. In the design shown in equation (1),the powers of all transmit signals are summed to obtain an overallpower. The digital power tracking signal is then obtained by taking thesquare root of the overall power. The scaling factor of √{square rootover (K)} accounts for conversion between power and voltage.

In another design, the digital power tracking signal may be computed asfollows:p(t)=√{square root over (I ₁ ²(t)+Q ₁ ²(t))}+ . . . +√{square root over(I _(K) ²(t)+Q _(K) ²(t))}.  Eq (2)

The quantity √{square root over (I_(k) ²(t)+Q_(k) ²(t))} denotes thevoltage of the k-th transmit signal in sample period t. In the designshown in equation (2), the voltage of each transmit signal is firstcomputed, and the voltages of all transmit signals are then summed toobtain the digital power tracking signal.

Equations (1) and (2) are two exemplary designs of computing the digitalpower tracking signal based on the I and Q samples for all transmitsignals being sent simultaneously. The digital power tracking signalcomputed in equation (1) or (2) has a bandwidth that approximates thebandwidth of the widest transmit signal (instead of the overallbandwidth of all transmit signals being sent simultaneously). Having thebandwidth of the power tracking signal being smaller than a modulationbandwidth may allow for a more efficient power tracking circuitry andmay also result in less noise being injected into PA 560 via the powersupply.

The digital power tracking signal may also be computed based on the Iand Q samples of the transmit signals in other manners, e.g., based onother equations or functions. In one design, the digital power trackingsignal may be generated based on the I and Q samples for all transmitsignals, without any filtering, e.g., as shown in equation (1) or (2).In another design, the digital power tracking signal may be filtered,e.g., with a lowpass filter having similar characteristics as lowpassfilters 544 and 545 in transmit circuit 540.

In one design, the digital power tracking signal may be computed in thesame manner (e.g., based on the same equation) regardless of the numberof transmit signals being sent simultaneously. In another design, thedigital power tracking signal may be computed in different manners(e.g., based on different equations) depending on the number of transmitsignals being sent simultaneously. The digital power tracking signal mayalso be computed in different manners depending on other factors such asthe transmit power levels of different transmit signals.

The techniques described herein for generating a power tracking supplyvoltage for multiple transmit signals may be used for various modulationtechniques. For example, the techniques may be used to generate a powertracking supply voltage for multiple transmit signals sentsimultaneously using orthogonal frequency division multiplexing (OFDM),SC-FDMA, CDMA, or some other modulation techniques. The techniques mayalso be used to generate a tracking power supply voltage for any numberof transmit signals being sent simultaneously.

FIG. 7A shows an example of power tracking for two transmit signals senton two non-contiguous carriers with SC-FDMA, e.g., for non-contiguousintra-band CA shown in FIG. 2B. The two transmit signals are sent on twocarriers separated by a 25 MHz gap, with each carrier having a bandwidthof 10 MHz. A plot 710 shows an output RF signal comprising the twotransmit signals and provided by PA 560 in FIG. 5 or 6. A plot 712 showsa power tracking signal provided by power tracker 582 in FIG. 5 or 6.The power tracking signal is computed based on I and Q samples for thetwo transmit signals in accordance with equation (1). As shown in FIG.7A, the power tracking signal closely follows the envelope of the outputRF signal. Hence, good performance and high efficiency may be achievedfor PA 560.

FIG. 7B shows an example of power tracking for three transmit signalssent on three non-contiguous carriers with OFDM, e.g., fornon-contiguous intra-band CA. The three transmit signals are sent onthree carriers, with each carrier having a bandwidth of 5 MHz and beingseparated by a 15 MHz gap to another carrier. A plot 720 shows an outputRF signal comprising the three transmit signals and provided by PA 560in FIG. 5 or 6. A plot 722 shows a power tracking signal provided bypower tracker 582 in FIG. 5 or 6. The power tracking signal is computedbased on I and Q samples for the three transmit signals in accordancewith equation (1). As shown in FIG. 7B, the power tracking signalfollows the envelope of the output RF signal. Hence, good performanceand high efficiency may be achieved for PA 560.

It can be shown that a power tracking supply voltage may also begenerated for multiple transmit signals sent on multiple carriers withCDMA. In general, the power tracking supply voltage can closely followthe envelope of the output RF signal when two transmit signals are sentsimultaneously, e.g., as shown in FIG. 7A. The power tracking supplyvoltage can approximate the envelope of the output RF signal when morethan two transmit signals are sent simultaneously, e.g., as shown inFIG. 7B.

Power supply generator 586 may generate a power supply voltage for PA560 based on a power tracking signal in various manners. Power supplygenerator 586 should generate the power supply voltage in an efficientmanner in order to conserve battery power of wireless device 110.

FIG. 8 shows a design of power supply generator 586 in FIGS. 5 and 6. Inthis design, power supply generator 586 includes a power trackingamplifier (PT Amp) 810, a switcher 820, a boost converter 830, and aninductor 822. Switcher 820 may also be referred to as a switching-modepower supply (SMPS). Switcher 820 receives a battery voltage (V_(BAT))and provides a first supply current (I_(SW)) comprising DC and lowfrequency components at node A. Inductor 822 stores current fromswitcher 820 and provides the stored current to node A on alternatingcycles. Boost converter 830 receives the V_(BAT) voltage and generates aboosted supply voltage (V_(BOOST)) that is higher than the V_(BAT)voltage. Power tracking amplifier 810 receives the analog power trackingsignal at its signal input, receives the V_(BAT) voltage and theV_(BOOST) voltage at its two power supply inputs, and provides a secondsupply current (I_(PT)) comprising high frequency components at node A.The PA supply current (I_(PA)) provided to power amplifier 560 includesthe I_(SW) current from switcher 820 and the I_(PT) current from powertracking amplifier 810. Power tracking amplifier 810 also provides theproper PA supply voltage (V_(PA)) at Node A for PA 560. The variouscircuits in power supply generator 586 are described in further detailbelow.

FIG. 9 shows a schematic diagram of a design of power tracking amplifier810 and switcher 820 within power supply generator 586 in FIG. 8. Withinpower tracking amplifier 810, an operational amplifier (op-amp) 910 hasits non-inverting input receiving the power tracking signal, itsinverting input coupled to an output of power tracking amplifier 810(which is node X), and its output coupled to an input of a class ABdriver 912. Driver 912 has its first output (R1) coupled to the gate ofa P-channel metal oxide semiconductor (PMOS) transistor 914 and itssecond output (R2) coupled to the gate of an N-channel metal oxidesemiconductor (NMOS) transistor 916. NMOS transistor 916 has its draincoupled to node X and its source coupled to circuit ground. PMOStransistor 914 has its drain coupled to node X and its source coupled tothe drains of PMOS transistors 918 and 920. PMOS transistor 918 has itsgate receiving a C1control signal and its source receiving the V_(BOOST)voltage. PMOS transistor 920 has its gate receiving a C2control signaland its source receiving the V_(BAT) voltage.

A current sensor 824 is coupled between node X and node A and senses theI_(PT) current provided by power tracking amplifier 810. Sensor 824passes most of the I_(PT) current to node A and provides a smallfraction of the I_(PT) current as a sensed current (I_(SEN)) to switcher820.

Within switcher 820, a current sense amplifier 930 has its input coupledto current sensor 824 and its output coupled to an input of a switcherdriver 932. Driver 932 has its first output (S1) coupled to the gate ofa PMOS transistor 934 and its second output (S2) coupled to the gate ofan NMOS transistor 936. NMOS transistor 936 has its drain coupled to anoutput of switcher 820 (which is node Y) and its source coupled tocircuit ground. PMOS transistor 934 has its drain coupled to node Y andits source receiving the V_(BAT) voltage. Inductor 822 is coupledbetween node A and node Y.

Switcher 820 operates as follows. Switcher 820 is in an ON state whencurrent sensor 824 senses a high output current from power trackingamplifier 810 and provides a low sensed voltage to driver 932. Driver932 then provides a low voltage to the gate of PMOS transistor 934 and alow voltage to the gate of NMOS transistor 936. PMOS transistor 934 isturned ON and couples the V_(BAT) voltage to inductor 822, which storesenergy from the V_(BAT) voltage. The current through inductor 822 risesduring the ON state, with the rate of the rise being dependent on (i)the difference between the V_(BAT) voltage and the V_(PA) voltage atnode A and (ii) the inductance of inductor 822. Conversely, switcher 820is in an OFF state when current sensor 824 senses a low output currentfrom power tracking amplifier 810 and provides a high sensed voltage todriver 932. Driver 932 then provides a high voltage to the gate of PMOStransistor 934 and a high voltage to the gate of NMOS transistor 936.NMOS transistor 936 is turned ON, and inductor 822 is coupled betweennode A and circuit ground. The current through inductor 822 falls duringthe OFF state, with the rate of the fall being dependent on the V_(PA)voltage at node A and the inductance of inductor 822. The V_(BAT)voltage thus provides current to PA 560 via inductor 822 during the ONstate, and inductor 120 provides its stored energy to PA 560 during theOFF state.

Power tracking amplifier 810 operates as follows. When the powertracking signal increases, the output of op-amp 910 increases, the R1output of driver 912 decreases and the R2 output of driver 912 decreasesuntil NMOS transistor 916 is almost turned OFF, and the output of powertracking amplifier 810 increases. The converse is true when the powertracking signal decreases. The negative feedback from the output ofpower tracking amplifier 810 to the inverting input of op-amp 910results in power tracking amplifier 810 having unity gain. Hence, theoutput of power tracking amplifier 810 follows the power trackingsignal, and the V_(PA) voltage is approximately equal to the powertracking signal. Driver 912 may be implemented with a class AB amplifierto improve efficiency, so that large output currents can be suppliedeven though the bias current in transistors 914 and 916 is low.

In one design, power tracking amplifier 810 operates based on theV_(BOOST) voltage only when needed and based on the V_(BAT) voltageduring the remaining time in order to improve efficiency. For example,power tracking amplifier 810 may provide approximately 85% of the powerbased on the V_(BAT) voltage and only approximately 15% of the powerbased on the V_(BOOST) voltage. When a high V_(PA) voltage is needed forPA 560 due to a large envelope of the output RF signal, the C1 controlsignal is at logic low, and the C2 control signal is at logic high. Inthis case, boost converter 830 is enabled and generates the V_(BOOST)voltage, PMOS transistor 918 is turned ON and provides the V_(BOOST)voltage to the source of PMOS transistor 914, and PMOS transistor 920 isturned OFF. Conversely, when a high V_(PA) voltage is not needed for PA560, the C1 control signal is at logic high, and the C2 control signalis at logic low. In this case, boost converter 830 is disabled, PMOStransistor 918 is turned OFF, and PMOS transistor 920 is turned ON andprovides the V_(BAT) voltage to the source of PMOS transistor 914.

A control signal generator 940 receives the power tracking signal andthe V_(BAT) voltage and generates the C1 and C2 control signals. The C1control signal is complementary to the C2 control signal. In one design,generator 940 generates the C1 and C2 control signals to select theV_(BOOST) voltage for power tracking amplifier 910 when the magnitude ofthe power tracking signal exceeds a first threshold. The first thresholdmay be a fixed threshold or may be determined based on the V_(BAT)voltage. In another design, generator 940 generates the C1 and C2control signals to select the V_(BOOST) voltage for power trackingamplifier 910 when the magnitude of the power tracking signal exceedsthe first threshold and the V_(BAT) voltage is below a second threshold.Generator 940 may also generate the C1 and C2 signals based on othersignals, other voltages, and/or other criteria.

Switcher 820 has high efficiency and delivers a majority of the supplycurrent for PA 560. Power tracking amplifier 810 operates as a linearstage and has relatively high bandwidth (e.g., in the MHz range).Switcher 820 operates to reduce the output current from power trackingamplifier 810, which improves overall efficiency.

FIG. 9 shows an exemplary design of switcher 820 and power trackingamplifier 810 in FIG. 1. Switcher 820 and power tracking amplifier 810may also be implemented in other manners. For example, power trackingamplifier 810 may be implemented as described in U.S. Pat. No.6,300,826, entitled “Apparatus and Method for Efficiently AmplifyingWideband Envelope Signals,” issued Oct. 9, 2001.

In an exemplary design, an apparatus (e.g., an integrated circuit, awireless device, a circuit module, etc.) may comprise a power trackerand a power supply generator. The power tracker (e.g., power tracker 582in FIG. 5) may determine a power tracking signal based on I and Qcomponents (e.g., I and Q samples) of a plurality of transmit signalsbeing sent simultaneously. The power supply generator (e.g., powersupply generator 586 in FIG. 5) may generate a power supply voltagebased on the power tracking signal.

In one design, the power tracker may determine an overall power of theplurality of transmit signals based on the I and Q components of theplurality of transmit signals, e.g., as I₁ ²(t)+Q₁ ²(t)+ . . . +I_(K)²(t)+Q_(K) ²(t). The power tracker may then determine the power trackingsignal based on the overall power of the plurality of transmit signals,e.g., as shown in equation (1). In another design, the power tracker maydetermine the power of each transmit signal based on the I and Qcomponents of that transmit signal, e.g., as I_(k) ²(t)+Q_(k) ²(t) forthe k-th transmit signal. The power tracker may then determine the powertracking signal based on the powers of the plurality of transmitsignals, e.g., as shown in equation (2). The power tracker may determinea voltage of each transmit signal based on the power of the transmitsignal, e.g., as √{square root over (I_(k) ²(t)+Q_(k) ²(t))}. The powertracker may then determine the power tracking signal based on voltagesof the plurality of transmit signals, e.g., as shown in equation (2).The power tracker may also determine the power tracking signal based onthe I and Q components of the plurality of transmit signals in othermanners. In one design, the plurality of transmit signals may be sent ona plurality of carriers at different frequencies. The power trackingsignal may have a bandwidth that is smaller than an overall bandwidth ofthe plurality of carriers.

In one design, the apparatus may comprise a plurality of transmitcircuits and a summer, e.g., as shown in FIG. 5. The plurality oftransmit circuits (e.g., transmit circuits 540 a to 540 k) may receivethe I and Q components of the plurality of transmit signals and mayprovide a plurality of upconverted RF signals. Each transmit circuit mayupconvert I and Q components of one transmit signal and provide acorresponding upconverted RF signal. The summer (e.g., summer 552) maysum the plurality of upconverted RF signals and provide a modulated RFsignal. In another design, the apparatus may comprise a transmit circuit(e.g., transmit circuit 540 in FIG. 6) that may receive a modulated IFsignal for the plurality of transmit signals and provide a modulated RFsignal. The modulated IF signal may be generated (e.g., by digitalmodulator 520 in FIG. 6) based on the I and Q components of theplurality of transmit signals. In an exemplary design, the apparatus mayfurther comprise a PA (e.g., PA 560 in FIGS. 5 and 6) that may amplifythe modulated RF signal based on the power supply voltage and provide anoutput RF signal.

In an exemplary design, the power supply generator may comprise a powertracking amplifier (e.g., power tracking amplifier 810 in FIGS. 8 and 9)that may receive the power tracking signal and generate the power supplyvoltage. The power supply generator may further comprise a switcherand/or a boost converter. The switcher (e.g., switcher 820 in FIGS. 8and 9) may sense a first current (e.g., the I_(PT) current) from thepower tracking amplifier and provide a second current (e.g., the I_(SW)current) for the power supply voltage based on the sensed first current.The boost converter (e.g., boost converter 830 in FIGS. 8 and 9) mayreceive a battery voltage and provide a boosted voltage for the powertracking amplifier. The power tracking amplifier may operate based onthe boosted voltage or the battery voltage.

FIG. 10 shows a design of a process 1000 for generating a power supplyvoltage with power tracking. A power tracking signal may be determinedbased on I and Q components of a plurality of transmit signals beingsent simultaneously (block 1012). In one design of block 1012, anoverall power of the plurality of transmit signals may be determinedbased on the I and Q components of the plurality of transmit signals.The power tracking signal may then be determined based on the overallpower of the plurality of transmit signals, e.g., as shown in equation(1). In another design of block 1012, the power of each transmit signalmay be determined based on the I and Q components of the transmitsignal. The power tracking signal may then be determined based on thepowers of the plurality of transmit signals, e.g., as shown in equation(2).

A power supply voltage may be generated based on the power trackingsignal (block 1014). In one design, the power supply voltage may begenerated with a amplifier (e.g., amplifier 810 in FIG. 9) that tracksthe power tracking signal. The power supply voltage may also begenerated based on a switcher and/or a boost converter.

A modulated RF signal may be generated based on the I and Q componentsof the plurality of transmit signals (block 1016). In one design, I andQ components of each transmit signal may be upconverted to obtain acorresponding upconverted RF signal. A plurality of upconverted RFsignals for the plurality of transmit signals may then be summed toobtain the modulated RF signal, e.g., as shown in FIG. 5. In anotherdesign, a modulated IF signal may be generated based on the I and Qcomponents of the plurality of transmit signals, e.g., as shown in FIG.6. The modulated IF signal may then be upconverted to obtain themodulated RF signal. In any case, the modulated RF signal may beamplified with a PA (e.g., PA 560 in FIGS. 5 and 6) operating based onthe power supply voltage to obtain an output RF signal (block 1018).

The power tracker and power supply generator described herein may beimplemented on an IC, an analog IC, an RFIC, a mixed-signal IC, an ASIC,a printed circuit board (PCB), an electronic device, etc. The powertracker and power supply generator may also be fabricated with variousIC process technologies such as complementary metal oxide semiconductor(CMOS), NMOS, PMOS, bipolar junction transistor (BJT), bipolar-CMOS(BiCMOS), silicon germanium (SiGe), gallium arsenide (GaAs), etc.

An apparatus implementing the power tracker and/or power supplygenerator described herein may be a stand-alone device or may be part ofa larger device. A device may be (i) a stand-alone IC, (ii) a set of oneor more ICs that may include memory ICs for storing data and/orinstructions, (iii) an RFIC such as an RF receiver (RFR) or an RFtransmitter/receiver (RTR), (iv) an ASIC such as a mobile station modem(MSM), (v) a module that may be embedded within other devices, (vi) areceiver, cellular phone, wireless device, handset, or mobile unit,(vii) etc.

In one or more exemplary designs, the functions described may beimplemented in hardware, software, firmware, or any combination thereof.If implemented in software, the functions may be stored on ortransmitted over as one or more instructions or code on acomputer-readable medium. Computer-readable media includes both computerstorage media and communication media including any medium thatfacilitates transfer of a computer program from one place to another. Astorage media may be any available media that can be accessed by acomputer. By way of example, and not limitation, such computer-readablemedia can comprise RAM, ROM, EEPROM, CD-ROM or other optical diskstorage, magnetic disk storage or other magnetic storage devices, or anyother medium that can be used to carry or store desired program code inthe form of instructions or data structures and that can be accessed bya computer. Also, any connection is properly termed a computer-readablemedium. For example, if the software is transmitted from a website,server, or other remote source using a coaxial cable, fiber optic cable,twisted pair, digital subscriber line (DSL), or wireless technologiessuch as infrared, radio, and microwave, then the coaxial cable, fiberoptic cable, twisted pair, DSL, or wireless technologies such asinfrared, radio, and microwave are included in the definition of medium.Disk and disc, as used herein, includes compact disc (CD), laser disc,optical disc, digital versatile disc (DVD), floppy disk and blu-ray discwhere disks usually reproduce data magnetically, while discs reproducedata optically with lasers. Combinations of the above should also beincluded within the scope of computer-readable media.

The previous description of the disclosure is provided to enable anyperson skilled in the art to make or use the disclosure. Variousmodifications to the disclosure will be readily apparent to thoseskilled in the art, and the generic principles defined herein may beapplied to other variations without departing from the scope of thedisclosure. Thus, the disclosure is not intended to be limited to theexamples and designs described herein but is to be accorded the widestscope consistent with the principles and novel features disclosedherein.

What is claimed is:
 1. An apparatus comprising: a power trackerconfigured to determine a single power tracking signal based on aplurality of inphase (I) and quadrature (Q) components of a plurality ofcarrier aggregated transmit signals being sent simultaneously, whereinthe power tracker receives the plurality of I and Q componentscorresponding to the plurality of carrier aggregated transmit signalsand generates the single power tracking signal based on a combination ofthe plurality of I and Q components, wherein the plurality of carrieraggregated transmit signals comprise Orthogonal Frequency DivisionMultiplexing (OFDM) or Single Carrier Frequency Division Multiple Access(SC-FDMA) signals; a power supply generator configured to generate asingle power supply voltage based on the single power tracking signal;and a power amplifier configured to receive the single power supplyvoltage and the plurality of carrier aggregated transmit signals beingsent simultaneously to produce a single output radio frequency (RF)signal.
 2. The apparatus of claim 1, wherein the power tracker isconfigured to: determine an overall power of the plurality of carrieraggregated transmit signals based on the I and Q components of theplurality of carrier aggregated transmit signals, and determine thesingle power tracking signal based on the overall power of the pluralityof carrier aggregated transmit signals.
 3. The apparatus of claim 1,wherein the power tracker is configured to: determine a power of eachtransmit signal in the plurality of carrier aggregated transmit signalsbased on the I and Q components of each transmit signal, and determinethe single power tracking signal based on a sum of said power of eachtransmit signal of the plurality of carrier aggregated transmit signals.4. The apparatus of claim 1, wherein the power tracker is configured to:determine a power of each transmit signal in the plurality of carrieraggregated transmit signals based on the I and Q components of eachtransmit signal, determine a voltage of each transmit signal based onthe power of each transmit signal, and determine the single powertracking signal based on said voltage of each transmit signal of theplurality of carrier aggregated transmit signals.
 5. The apparatus ofclaim 1, further comprising: a plurality of transmit circuits configuredto receive the I and Q components of the plurality of carrier aggregatedtransmit signals and provide a plurality of upconverted RF signals, eachtransmit circuit configured to upconvert I and Q components of one ofthe plurality of carrier aggregated transmit signals and provide acorresponding upconverted RF signal, and a summer configured to sum theplurality of upconverted RF signals and provide the plurality of carrieraggregated transmit signals to the power amplifier.
 6. The apparatus ofclaim 1, further comprising: a transmit circuit configured to receive amodulated intermediate frequency (IF) signal and provide the pluralityof carrier aggregated transmit signals to the power amplifier, themodulated IF signal being generated based on the I and Q components ofthe plurality of carrier aggregated transmit signals.
 7. The apparatusof claim 1, the power supply generator comprising: a power trackingamplifier configured to receive the power tracking signal and generatethe power supply voltage.
 8. The apparatus of claim 7, the power supplygenerator further comprising: a switcher configured to sense a firstcurrent from the power tracking amplifier and provide a second currentfor the power supply voltage based on the sensed first current.
 9. Theapparatus of claim 7, the power supply generator further comprising: aboost converter configured to receive a battery voltage and provide aboosted voltage for the power tracking amplifier.
 10. The apparatus ofclaim 9, wherein the power tracking amplifier operates based on theboosted voltage or the battery voltage.
 11. The apparatus of claim 1,wherein the plurality of carrier aggregated transmit signals are sent ona plurality of carriers at different frequencies.
 12. The apparatus ofclaim 11, wherein the single power tracking signal has a bandwidth thatis smaller than an overall bandwidth of the plurality of carriers. 13.The apparatus of claim 1, wherein the carrier aggregated transmitsignals are intra-band carrier aggregated transmit signals.
 14. Theapparatus of claim 13, wherein the intra-band carrier aggregatedtransmit signals are contiguous.
 15. The apparatus of claim 13, whereinthe intra-band carrier aggregated transmit signals are non-contiguous.16. The apparatus of claim 1, wherein the power tracker is configured todetermine the single power tracking signal based on functionscomprising: squaring each of the plurality of inphase (I) and quadrature(Q) components to produce a plurality of I² and Q² values; summing theplurality of I² and Q² values to produce an overall power; and takingthe square root of the overall power.
 17. The apparatus of claim 1,wherein the power tracker is configured to determine the single powertracking signal based on functions comprising: calculating √{square rootover (I_(k) ²(t)+Q_(k) ²(t))} corresponding to K inphase (I) andquadrature (Q) components to produce K voltages; and summing the Kvoltages.
 18. A method comprising: determining a single power trackingsignal based on a plurality of inphase (I) and quadrature (Q) componentsof a plurality of carrier aggregated transmit signals being sentsimultaneously, wherein a power tracker receives the plurality of I andQ components corresponding to the plurality of carrier aggregatedtransmit signals and generates the single power tracking signal based ona combination of the plurality of I and Q components, wherein theplurality of carrier aggregated transmit signals comprise OrthogonalFrequency Division Multiplexing (OFDM) or Single Carrier FrequencyDivision Multiple Access (SC-FDMA) signals; generating a single powersupply voltage based on the single power tracking signal; and receivingthe single power supply voltage and the plurality of carrier aggregatedtransmit signals being sent simultaneously in a power amplifier andproducing a single output radio frequency (RF) signal.
 19. The method ofclaim 18, wherein the determining the single power tracking signalcomprises: determining an overall power of the plurality of carrieraggregated transmit signals based on the I and Q components of theplurality of carrier aggregated transmit signals, and determining thesingle power tracking signal based on the overall power of the pluralityof carrier aggregated transmit signals.
 20. The method of claim 18,wherein the determining the single power tracking signal comprises:determining a power of each transmit signal in the plurality of carrieraggregated transmit signals based on the I and Q components of eachtransmit signal, and determining the single power tracking signal basedon a sum of said power of each transmit signal of the plurality ofcarrier aggregated transmit signals.
 21. The method of claim 18, furthercomprising: receiving the I and Q components of the plurality of carrieraggregated transmit signals in a plurality of transmit circuits andproviding a plurality of upconverted RF signals from the plurality oftransmit circuits, each transmit circuit upconverting I and Q componentsof one of the plurality of carrier aggregated transmit signals andproviding a corresponding upconverted RF signal, and summing theplurality of upconverted RF signals and providing the plurality ofcarrier aggregated transmit signals to the power amplifier.
 22. Themethod of claim 18, further comprising: receiving a modulatedintermediate frequency (IF) signal in a transmit circuit and providingthe plurality of carrier aggregated transmit signals to the poweramplifier from the transmit circuit, the modulated IF signal beinggenerated based on the I and Q components of the plurality of carrieraggregated transmit signals.
 23. The method of claim 18, wherein thecarrier aggregated transmit signals are intra-band carrier aggregatedtransmit signals.
 24. The method of claim 23, wherein the intra-bandcarrier aggregated transmit signals are contiguous.
 25. The method ofclaim 23 wherein the intra-band carrier aggregated transmit signals arenon-contiguous.
 26. The method of claim 18, wherein determining thesingle power tracking signal comprises: squaring each of the pluralityof inphase (I) and quadrature (Q) components to produce a plurality ofI² and Q² values; summing the plurality of I² and Q² values to producean overall power; and taking the square root of the overall power. 27.The method of claim 18, wherein determining the single power trackingsignal comprises: calculating √{square root over (I_(k) ²(t) +Q_(k)²(t))} corresponding to K inphase (I) and quadrature (Q) components toproduce K voltages; and summing the voltages.
 28. An apparatuscomprising: means for determining a single power tracking signal basedon a plurality of inphase (I) and quadrature (Q) components of aplurality of carrier aggregated transmit signals being sentsimultaneously, wherein a power tracker receives the plurality of I andQ components corresponding to the plurality of carrier aggregatedtransmit signals and generates the single power tracking signal based ona combination of the plurality of I and Q components, wherein theplurality of carrier aggregated transmit signals comprise OrthogonalFrequency Division Multiplexing (OFDM) or Single Carrier FrequencyDivision Multiple Access (SC-FDMA) signals; means for generating asingle power supply voltage based on the single power tracking signal;and means for receiving the single power supply voltage and theplurality of carrier aggregated transmit signals being sentsimultaneously and producing a single output radio frequency (RF)signal.
 29. The apparatus of claim 28, wherein the means for determiningthe single power tracking signal comprises: means for determining anoverall power of the plurality of carrier aggregated transmit signalsbased on the I and Q components of the plurality of carrier aggregatedtransmit signals, and means for determining the single power trackingsignal based on the overall power of the plurality of carrier aggregatedtransmit signals.
 30. The apparatus of claim 28, wherein the means fordetermining the single power tracking signal comprises: means fordetermining a power of each transmit signal in the plurality of carrieraggregated transmit signals based on the I and Q components of eachtransmit signal, and means for determining the single power trackingsignal based on a sum of said power of each transmit signal of theplurality of carrier aggregated transmit signals.
 31. The apparatus ofclaim 28, further comprising: means for receiving the I and Q componentsof the plurality of carrier aggregated transmit signals and separatelyupconverting the I and Q components of the plurality of carrieraggregated transmit signals to provide a plurality of upconverted RFsignals, and means for summing the plurality of upconverted RF signalsand providing the plurality of carrier aggregated transmit signals to apower amplifier.
 32. The apparatus of claim 28, further comprising:means for receiving a modulated intermediate frequency (IF) signal andproviding the plurality of carrier aggregated transmit signals to apower amplifier, the modulated IF signal being generated based on the Iand Q components of the plurality of carrier aggregated transmitsignals.
 33. A non-transitory computer-readable medium comprisinginstructions, that when executed by a processor, cause the processor to:determine a single power tracking signal based on a plurality of inphase(I) and quadrature (Q) components of a plurality of carrier aggregatedtransmit signals being sent simultaneously, wherein a power trackerreceives the plurality of I and Q components corresponding to theplurality of carrier aggregated transmit signals and generates thesingle power tracking signal based on a combination of the plurality ofI and Q components, wherein the plurality of carrier aggregated transmitsignals comprise Orthogonal Frequency Division Multiplexing (OFDM) orSingle Carrier Frequency Division Multiple Access (SC-FDMA) signals;generate a single power supply voltage based on the single powertracking signal; and receive the single power supply voltage and theplurality of carrier aggregated transmit signals being sentsimultaneously in a power amplifier to produce a single output radiofrequency (RF) signal.